# Serum iron

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> Source: https://en.wikipedia.org/wiki/Serum_iron
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| MedlinePlus     = 003488
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'''[Serum](/source/Blood_plasma) iron''' is a [medical](/source/medicine) laboratory test that measures the amount of circulating [iron](/source/iron) that is bound to [transferrin](/source/transferrin) and freely circulate in the blood. Clinicians order this laboratory test when they are concerned about [iron deficiency](/source/Iron_deficiency_(medicine)), which can cause [anemia](/source/anemia) and other problems. 65% of the iron in the body is bound up in [hemoglobin](/source/hemoglobin) molecules in [red blood cell](/source/red_blood_cell)s. About 4% is bound up in [myoglobin](/source/myoglobin) molecules. Around 30% of the iron in the body is stored as [ferritin](/source/ferritin) or [hemosiderin](/source/hemosiderin) in the [spleen](/source/spleen), the [bone marrow](/source/bone_marrow) and the [liver](/source/liver). Small amounts of iron can be found in other molecules in cells throughout the body. None of this iron is directly accessible by testing the serum.{{cn|date=November 2021}}

However, some iron is circulating in the serum. Transferrin is a molecule produced by the liver that binds one or two iron(III) [ions](/source/ions), i.e. ferric iron, Fe<sup>3+</sup>; transferrin is essential if stored iron is to be moved and used. Most of the time, about 30% of the available sites on the transferrin molecule are filled. The test for serum iron uses blood drawn from [vein](/source/vein)s to measure the iron ions that are bound to transferrin and circulating in the blood. This test should be done after 12 hours of fasting. The extent to which sites on transferrin molecules are filled by iron ions can be another helpful clinical indicator, known as [percent transferrin saturation](/source/percent_transferrin_saturation). Another lab test saturates the sample to measure the total amount of transferrin; this test is called [total iron-binding capacity](/source/total_iron-binding_capacity) (TIBC). These three tests are generally done at the same time, and taken together are an important part of the diagnostic process for conditions such as [anemia](/source/anemia), [iron deficiency anemia](/source/iron_deficiency_anemia), [anemia of chronic disease](/source/anemia_of_chronic_disease) and [haemochromatosis](/source/haemochromatosis).{{citation needed|date=July 2020}}

==Normal values==
Normal [reference ranges](/source/reference_ranges_for_blood_tests) are:
* Serum iron:<ref name=uimc>[http://uimc.discoveryhospital.com/main.php?t=enc&id=1456 Serum Iron] {{webarchive|url=https://web.archive.org/web/20061028111833/http://uimc.discoveryhospital.com/main.php?t=enc&id=1456 |date=2006-10-28 }}. University of Illinois Medical Center. Accessed July 6, 2006.</ref>
** Men: 65 to 176  μg/dL
** Women: 50 to 170 μg/dL
** Newborns: 100 to 250 μg/dL
** Children: 50 to 120 μg/dL
* [TIBC](/source/Total_iron-binding_capacity): 240–450 μg/dL <ref name=uimc/>
* [Transferrin saturation](/source/Transferrin_saturation): 20–50% <ref name=uimc/>

μg/dL = [microgram](/source/microgram)s per [deciliter](/source/deciliter).

Laboratories often use different units and "normal" may vary by population and the lab techniques used; look at the individual laboratory [reference values](/source/reference_values) to interpret a specific test (for instance, your own).

[[File:Blood values sorted by mass and molar concentration.png|thumb|550px|center|[Reference ranges for blood tests](/source/Reference_ranges_for_blood_tests), comparing blood content of iron and related compounds (shown in brown and orange) with other constituents.]]

==See also==
* [Human iron metabolism](/source/Human_iron_metabolism)

==References==
{{reflist}}

==Further reading==
* Medline Plus Medical Encyclopedia: [https://www.medlineplus.gov/ency/article/003488.htm Serum Iron].

{{Blood tests}}

Category:Blood tests
Category:Iron metabolism
Category:Clinical chemistry

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Adapted from the Wikipedia article [Serum iron](https://en.wikipedia.org/wiki/Serum_iron) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Serum_iron?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.